Buckling restrained brace

ABSTRACT

A buckling restrained brace is for connection between two connecting plates of a framework, and includes a restraining unit and an axial member. The axial member includes a middle section surrounded by the restraining unit, two first coupling sections, and two second coupling sections. The first coupling sections are connected respectively and perpendicularly to opposite longitudinal end portions of the middle section. Each first coupling section has a portion exposed from a respective one of longitudinal ends of the restraining unit, and is formed with a first coupling groove for engaging a respective one of the connecting plates. The second coupling sections are connected respectively and perpendicularly to the opposite longitudinal ends of the middle section. Each second coupling section has a portion exposed from a respective one of the longitudinal end portions of the restraining unit, and is formed with a second coupling groove for engaging a respective one of the connecting plates.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priorities of Taiwanese Application Nos. 099108880 and 099205208, filed on Mar. 25, 2010.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a buckling restrained brace, more particularly to a buckling restrained brace that is adapted to be connected fixedly between two connecting plates of a framework of a building.

2. Description of the Related Art

A buckling restrained brace is generally used in a steel framework of a building for absorbing vibration energy generated by an earthquake so as to minimize damage to the framework resulting from the shock of the earthquake.

As shown in FIG. 1, a conventional buckling restrained brace 1 is provided between two connecting plates 14 of a steel framework 13 of a building, and includes an axial member 11 and a restraining unit 12 that surrounds the axial member 11. The axial member 11 has end portions longitudinally opposite to each other and connected respectively to the connecting plates 14 of the steel framework 13.

However, the restraining unit 12 generally has a square or round cross-section, and the conventional buckling restrained brace 1 has a relatively heavy weight and a relatively large volume, thereby resulting in inconvenience when being assembled to the steel framework 13, and occupying a relatively large space within the building.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a buckling restrained brace that can alleviate the abovementioned drawbacks of the conventional buckling restrained brace.

Another object of the present invention is to provide an axial member adapted for use in a buckling restrained brace.

Yet another object of the present invention is to provide a method for making a buckling restrained brace.

Accordingly, a buckling restrained brace of the present invention is adapted to be connected fixedly between two connecting plates of a framework of a building. The buckling restrained brace comprises a rigid restraining unit extending in an axial direction and having opposite longitudinal ends, and an axial member. The axial member includes a middle section, a pair of first coupling sections, and a pair of second coupling sections. The middle section extends in the axial direction and is surrounded by the restraining unit. The first coupling sections are connected respectively and perpendicularly to opposite longitudinal end portions of the middle section. Each of the first coupling sections extends in the axial direction, has at least a portion exposed from a respective one of the longitudinal ends of the restraining unit, and is formed with a first coupling groove adapted for engaging a respective one of the connecting plates. The second coupling sections are connected respectively and perpendicularly to the opposite longitudinal end portions of the middle section. Each of the second coupling sections extends in the axial direction, is spaced apart from a corresponding one of the first coupling sections in a first transverse direction transverse to the axial direction, has at least a portion exposed from a respective one of the longitudinal ends of the restraining unit, and is formed with a second coupling groove adapted for engaging a respective one of the connecting plates.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments with reference to the accompanying drawings, of which:

FIG. 1 is a schematic view of a conventional buckling restrained brace connected to a steel framework;

FIG. 2 is a schematic side view of a first preferred embodiment of a buckling restrained brace according to the invention;

FIG. 3 is another schematic side view of the first preferred embodiment;

FIG. 4 is a sectional view of the first preferred embodiment taken along line 91-91 in FIG. 3;

FIG. 5 is another sectional view of the first preferred embodiment taken along line 92-92 in FIG. 3;

FIG. 6 is a flow chart of a method of making the first preferred embodiment;

FIG. 7 is a perspective view of a surrounding member of the first preferred embodiment;

FIG. 8 is an exploded perspective view of the first preferred embodiment;

FIG. 9 is an assembled perspective view of the first preferred embodiment;

FIG. 10 is a schematic side view of a second preferred embodiment of the buckling restrained brace according to the invention;

FIG. 11 is another schematic side view of the second preferred embodiment;

FIG. 12 is a sectional view of the second preferred embodiment taken along line 93-93 in FIG. 10;

FIG. 13 is another sectional view of the second preferred embodiment taken along line 94-94 in FIG. 10;

FIG. 14 is a flow chart of a method of making the second preferred embodiment;

FIG. 15 is a perspective view of a surrounding member of the second preferred embodiment;

FIG. 16 is an exploded perspective view of the second preferred embodiment;

FIG. 17 is an assembled perspective view of the second preferred embodiment;

FIG. 18 is a schematic side view of a third preferred embodiment of the buckling restrained brace according to the invention;

FIG. 19 is another schematic side view of the third preferred embodiment;

FIG. 20 is a sectional view of the third preferred embodiment taken along line 95-95 in FIG. 18;

FIG. 21 is another sectional view of the third preferred embodiment taken along line 96-96 in FIG. 18;

FIG. 22 is a flow chart of a method of making the third preferred embodiment;

FIG. 23 is a perspective view of a surrounding member of the third preferred embodiment;

FIG. 24 is an exploded perspective view of the third preferred embodiment; and

FIG. 25 is an assembled perspective view of the third preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before the present invention is described in greater detail, it should be noted that like elements are denoted by the same reference numerals throughout the disclosure.

Referring to FIG. 2, the first preferred embodiment of a buckling restrained brace 201 according to the present invention is adapted to be connected fixedly between two connecting plates 9 of a steel framework of a building. The buckling restrained brace 201 comprises a rigid restraining unit 3 and an axial member 4.

Further referring to FIGS. 3 to 5, the restraining unit 3 includes a surrounding member 31 extending in an axial direction (X) and having opposite longitudinal ends. In this embodiment, the surrounding member 31 is formed with an inner surrounding surface 311 (see FIG. 7).

The axial member 4 includes a middle section 41, a pair of first coupling sections 42, and a pair of second coupling sections 43.

The middle section 41 extends in the axial direction (X), and is surrounded by the surrounding member 31 of the restraining unit 3 (i.e., the inner surrounding surface 311 of the surrounding member 31 faces the middle section 41). With further reference to FIG. 8, the middle section 41 has two longitudinal end portions 415 opposite to each other in the axial direction (X) and exposed respectively from the longitudinal ends of the surrounding member 31. The middle section 41 further has a main portion 416 disposed between the end portions 415, and two converging portions 417. One of the converging portions 417 interconnects the main portion 416 and one of the end portions 415, and the other one of the converging portions 417 interconnects the main portion 416 and the other one of the end portions 415. Each of the converging portions 417 converges from a corresponding one of the end portions 415 toward the main portion 416. The restraining unit 3 further includes a curable material 32 filled between the surrounding member 31 and the middle section 41.

The first coupling sections 42 are connected respectively and perpendicularly to the longitudinal end portions of the middle section 41. The second coupling sections 43 are connected respectively and perpendicularly to the longitudinal end portions of the middle section 41. Each of the first and second coupling sections 42, 43 extends in the axial direction (X). Each of the second coupling sections 43 is spaced apart from a corresponding one of the first coupling sections 42 in a first transverse direction (Y) transverse to the axial direction (X). The middle section 41 is formed as an elongated plate, which is formed with first and second side surfaces 411, 412 opposite to each other in a second transverse direction (Z) transverse to the axial direction (X) and the first transverse direction (Y). In this embodiment, each of the first and second coupling sections 42, 43 has a first coupling segment 441 that is connected to the first side surface 411 of the middle section 41, and that has an exposed part 4411 exposed from a respective one of the longitudinal ends of the surrounding member 31, and a connecting part 4412 connected to the exposed part 4411 and surrounded by the surrounding member 31. In this embodiment, each of the first and second coupling sections 42, 43 further has a second coupling segment 442 that is connected to the second side surface 412 of the middle section 41, and that has an exposed part 4421 exposed from a respective one of the longitudinal ends of the surrounding member 31, and a connecting part 4922 connected to the exposed part 4421 and surrounded by the surrounding member 31. The exposed part 4411 of the first coupling segment 441 of each of the first coupling sections 42 cooperates with the exposed part 4421 of the second coupling segment 442 of the corresponding one of the first coupling sections 42 to define a first coupling groove 443 (see FIG. 9). The exposed part 4411 of the first coupling segment 441 of each of the second coupling sections 93 cooperates with the exposed part 4421 of the second coupling segment 442 of the corresponding one of the second coupling sections 43 to define a second coupling groove 444. Each of the first and second coupling segments 441, 442 of the first and second coupling sections 42, 43 is in contact with the inner surrounding surface 311 of the surrounding member 31.

When connecting to the steel framework of the building, the buckling restrained brace 201 is disposed between the connecting plates 9 with the middle section 41 of the axial member 4 being coplanar with the connecting plates 9 and with each of the first and second coupling sections 42, 43 being perpendicular to the connecting plates 9, such that each of the first and second coupling grooves 443, 444 engages a respective one of the connecting plates 9 (i.e., one of the first engaging grooves 443 and a corresponding one of the second engaging grooves 444 engage one of the connecting plates 9, while the other one of the first engaging grooves 443 and a corresponding one of the second engaging grooves 444 engage the other one of the connecting plates 9). As such, the surrounding member 31 can be designed to have a rectangular cross-section as clearly illustrated in FIG. 7, thereby resulting in a smaller volume thereof than the conventional buckling restrained brace 1 illustrated in FIG. 1.

The connecting part 4412, 4422 of each of the first and second coupling segments 441, 442 has an end surface opposite to the exposed part 4411, 4421 of a corresponding one of the first and second coupling segments 441, 442 in the axial direction (X) and inclining toward the exposed part 4411, 4421 of the corresponding one of the first and second coupling segments 441, 442. The presence of the converging portions 417 of the middle section 41 as well as the end surfaces of the first and second segments 441, 442 strengthens effectively the stiffness and the strength of two ends of the axial member 4 so that the axial member 4 can have uniform stress distribution.

As shown in FIG. 6, a method of making the buckling restrained brace 201 of this invention comprises steps 901 to 904.

Referring to FIG. 7, the step 901 is to prepare the hollow surrounding member 31 that is made of steel and that has a rectangular cross-section.

As shown in FIG. 8, the step 902 is to prepare the axial member 4 that extends in the axial direction (X) and that includes a middle section 41, two pairs of first coupling segments 441, and two pairs of second coupling segments 442. Each pair of the first coupling segments 441 extend in the axial direction (X) and are connected perpendicularly to the first side surface 411 of the middle section 41 at a respective one of the longitudinal end portions of the middle section 41. Each pair of the second coupling segments 442 extend in the axial direction (X) and are connected perpendicularly to the second side surface 412 of the middle section 41 at a respective one of the longitudinal end portions of the middle section 41. The exposed part 4411, 4421 of each of the first coupling segments 441 cooperates with the exposed part 4411, 4421 of the corresponding one of the second coupling segments 442 to define the first and second coupling grooves 443, 444 (see FIG. 9) therebetween. In this embodiment, the middle section 41, and the first and second coupling segments 441, 442 are made of steel.

As shown in FIG. 9, the step 903 is to extend the axial member 4 through the surrounding member 31 such that the exposed parts 4411, 4421 and the first and second coupling grooves 443, 444 are exposed from the surrounding member 31, and that the connecting part 4412, 4422 of each of the first and second coupling segments 441, 442 are in contact with the inner surrounding surface 311 of the surrounding member 31 so as to stabilize the structure and to strengthen the structural strength of the buckling restrained brace 201.

The step 904 is to fill the curable material 32 between the surrounding member 31 and the middle section 41 of the axial member 4. In this embodiment, the curable material 32 may be structural concrete or epoxy resin.

As shown in FIG. 10, the second preferred embodiment of the buckling restrained brace 202 according to the present invention has a structure similar to that of the first embodiment. The main difference between this embodiment and the previous embodiment resides in the configuration of the axial member.

As further shown in FIGS. 11 to 13, in this embodiment, the axial member 6 includes a middle section 61 extending in the axial direction (X) and surrounded by the surrounding member 31, a pair of first coupling sections 62 and a pair of second coupling sections 63.

The first coupling sections 62 are connected respectively and perpendicularly to opposite longitudinal end portions of the middle section 61. With further reference to FIG. 16, each of the first coupling sections 62 has a portion exposed from a respective one of the longitudinal ends of the surrounding member 31 and formed with a first coupling groove 642. The second coupling sections 63 are connected respectively and perpendicularly to the opposite longitudinal end portions of the middle section 61. Each of the second coupling sections 63 is spaced apart from a corresponding one of the first coupling sections 62 in the first transverse direction (Y), and has a portion exposed from a respective one of the longitudinal ends of the surrounding member 31 and formed with a second coupling groove 643.

The middle section 61 has an intermediate segment 611 and first and second lateral segments 612, 613 connected respectively and perpendicularly to opposite lateral ends of the intermediate segment 611 in the first transverse direction (Y) such that the middle section 61 has an H-shaped cross-section (see FIG. 13). The intermediate segment 611 is formed with an elongated slot 641 extending in the axial direction (X). The first lateral segment 612 interconnects integrally the first coupling sections 62 to form a first plate 68 (see FIG. 16), and the second lateral segment 613 interconnects integrally the second coupling sections 63 to form a second plate 69 (see FIG. 16). Each of the first and second plates 68, 69 has an axial length longer than that of the intermediate segment 611. Each of the first and second coupling sections 62, 63 has opposite distal edges in the second transverse direction (Z) that are in contact with the inner surrounding surface 311 of the surrounding member 31 (see FIG. 15).

In this embodiment, each of the first coupling sections 62 has a maximum width in the second transverse direction (Z) that is larger than that of the first lateral segment 612, and includes a converging part 621 that is connected integrally to and converges toward the first lateral segment 612. Each of the second coupling sections 63 has a maximum width in the second transverse direction (Z) that is larger than that of the second lateral segment 613, and includes a converging part 631 that is connected integrally to and converges toward the second lateral segment 613. Therefore, the stiffness and the strength of two ends of the axial member 6 can be strengthened. Preferably, the elongated slot 641 formed in the intermediate segment 611 of the middle section 61 weakens the structural strength of the middle section 61, so that the buckling restrained brace 202 of this embodiment can have uniform stress distribution.

As shown in FIG. 14, a method of making the buckling restrained brace 202 of this invention comprises steps 905 to 908.

Referring to FIG. 15, the step 905 is to prepare the hollow surrounding member 31 that is made of steel and that has a rectangular cross-section.

Referring to FIG. 16, the step 906 is to prepare the axial member 6 composed of the middle section 61 that is formed with the elongated slot 641, and the first and second plates 68, 69 that have the first and second coupling sections 62, 63 formed with the first and second coupling grooves 642, 643. In this embodiment, the middle section 61 and the first and second plates 68, 69 are made of steel and welded integrally together.

As shown in FIG. 17, the step 907 is to extend the axial member 6 through the surrounding member 31 such that a portion of each of the first and second coupling sections 62, 63 and the first and second coupling grooves 642, 643 is exposed from the surrounding member 31, and that the distal edges of each of the first and second coupling sections 62, 63 are in contact with the inner surrounding surface 311 of the surrounding member 31 so as to stabilize the structure and to strengthen the structural strength of the buckling restrained brace 202.

The step 908 is to fill the curable material 32 between the surrounding member 31 and the middle section 61 of the axial member 6.

As shown in FIG. 18, the third preferred embodiment of the buckling restrained brace 203 according to the present invention has a structure similar to that of the second preferred embodiment. The main difference between this embodiment and the previous embodiment resides in the configuration of the axial member.

As further shown in FIGS. 19 to 21, in this embodiment, the axial member 8 includes a middle section 81 extending in the axial direction (X) and surrounded by the surrounding member 31, a pair of first coupling sections 82 and a pair of second coupling sections 83.

The middle section 81 has a first lateral segment 811 interconnecting integrally the first coupling sections 82 to form a first plate 88 (see FIG. 24). Each of the first coupling sections 82 has a portion exposed from a respective one of the longitudinal ends of the surrounding member 31 and formed with a first coupling groove 841. The second lateral segment 812 is spaced apart from the first lateral segment 811 in the first transverse direction (Y) and interconnects integrally the second coupling sections 83 to form a second plate 89 (see FIG. 24). Each of the second coupling sections 83 has a portion exposed from a respective one of the longitudinal ends of the surrounding member 31 and formed with a second coupling groove 842. Each of the first and second coupling sections 82, 83 has opposite distal edges in the second transverse direction (Z) that are in contact with the inner surrounding surface 311 of the surrounding member 31 (see FIG. 23).

In this embodiment, each of the first coupling sections 82 has a maximum width in the second transverse direction (Z) that is larger than that of the first lateral segment 811, and includes a converging part 821 that is connected integrally to and converges toward the first lateral segment 811. Each of the second coupling sections 83 has a maximum width in the second transverse direction (Z) that is larger than that of the second lateral segment 812, and includes a converging part 831 that is connected integrally to and converges toward the second lateral segment 812. The third preferred embodiment has the same advantages as those of the second preferred embodiment.

As shown in FIG. 22, a method of making the buckling restrained brace 203 of this invention comprises steps 909 to 912.

Referring to FIG. 23, the step 909 is to prepare the hollow surrounding member 31 that is made of steel and that has a rectangular cross-section.

Referring to FIG. 24, the step 910 is to prepare the axial member 8 including the first and second plates 88, 89 that are formed with the first and second coupling sections 82, 83 formed with the first and second coupling grooves 841, 842. In this embodiment, the first and second plates 88, 89 are made of steel.

As shown in FIG. 25, the step 911 is to extend the axial member 8 through the surrounding member 31 such that a portion of each of the first and second coupling sections 82, 83 and the first and second coupling grooves 841, 842 is exposed from the surrounding member 31, and that the distal edges of each of the first and second coupling sections 82, 83 are in contact with the inner surrounding surface 311 of the surrounding member 31.

The step 912 is to fill the curable material 32 between the surrounding member 31 and the first and second plates 88, 89.

While the present invention has been described in connection with what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements. 

1. A buckling restrained brace adapted to be connected fixedly between two connecting plates of a framework of a building, said buckling restrained brace comprising: a rigid restraining unit extending in an axial direction and having opposite longitudinal ends; and an axial member including a middle section that extends in the axial direction and that is surrounded by said restraining unit, a pair of first coupling sections that are connected respectively and perpendicularly to opposite longitudinal end portions of said middle section, each of said first coupling sections extending in the axial direction, having at least a portion exposed from a respective one of said longitudinal ends of said restraining unit, and being formed with a first coupling groove adapted for engaging a respective one of the connecting plates, and a pair of second coupling sections that are connected respectively and perpendicularly to said opposite longitudinal end portions of said middle section, each of said second coupling sections extending in the axial direction, being spaced apart from a corresponding one of said first coupling sections in a first transverse direction transverse to the axial direction, having at least a portion exposed from a respective one of said longitudinal ends of said restraining unit, and being formed with a second coupling groove adapted for engaging a respective one of the connecting plates.
 2. The buckling restrained brace as claimed in claim 1, wherein: said middle section of said axial member is formed as an elongated plate, said elongated plate being formed with first and second side surfaces that are opposite to each other in a second transverse direction transverse to the axial direction and the first transverse direction; and each of said first and second coupling sections of said axial member has a first coupling segment that is connected to said first side surface of said middle section, and that has an exposed part exposed from a corresponding one of said longitudinal ends of said restraining unit, and a second coupling segment that is connected to said second side surface of said middle section, and that has an exposed part exposed from a corresponding one of said longitudinal ends of said restraining unit, and cooperating with said exposed part of said first coupling segment to define a corresponding one of said first and second coupling grooves.
 3. The buckling restrained brace as claimed in claim 2, wherein each of said first and second coupling segments of said first and second coupling sections of said axial member further has a connecting part connected to said exposed part of a corresponding one of said first and second coupling segments and surrounded by said restraining unit.
 4. The buckling restrained brace as claimed in claim 3, wherein said connecting part of each of said first and second coupling segments of said first and second coupling sections of said axial member has an end surface opposite to said exposed part of a corresponding one of said first and second coupling segments in the axial direction and inclining toward said exposed part of the corresponding one of said first and second coupling segments.
 5. The buckling restrained brace as claimed in claim 2, wherein said end portions of said middle section of said axial member are exposed respectively from said longitudinal ends of said restraining unit.
 6. The buckling restrained brace as claimed in claim 5, wherein said middle section of said axial member further has a main portion disposed between said end portions, and two converging portions, one of said converging portions interconnecting said main portion and one of said end portions, the other one of said converging portions interconnecting said main portion and the other one of said end portions, each of said converging portions converging from a corresponding one of said end portions toward said main portion.
 7. The buckling restrained brace as claimed in claim 2, wherein said restraining unit includes a rigid surrounding member surrounding said axial member and having an inner surrounding surface that faces said axial member, each of said first and second coupling segments of said first and second coupling sections of said axial member being in contact with said inner surrounding surface of said surrounding member.
 8. The buckling restrained brace as claimed in claim 1, wherein said restraining unit has a rectangular cross-section.
 9. The buckling restrained brace as claimed in claim 1, wherein said middle section of said axial member has an intermediate segment and first and second lateral segments connected respectively to opposite lateral ends of said intermediate segment in the first transverse direction, said first lateral segment interconnecting integrally said first coupling sections to form a first plate, said second lateral segment interconnecting integrally said second coupling sections to form a second plate.
 10. The buckling restrained brace as claimed in claim 9, wherein: each of said first coupling sections of said axial member has a maximum width in a second transverse direction transverse to the axial direction and the first transverse direction that is larger than that of said first lateral segment of said middle section of said axial member, and includes a converging part that is connected integrally to said first lateral segment and that converges toward said first lateral segment; and each of said second coupling sections of said axial member has a maximum width in the second transverse direction that is larger than that of said second lateral segment of said middle section, and a converging part that is connected integrally to said second lateral segment and that converges toward said second lateral segment.
 11. The buckling restrained brace as claimed in claim 9, wherein each of said first and second lateral segments of said middle section of said axial member is connected perpendicularly to said intermediate segment of said middle section of said axial member such that said middle section has an H-shaped cross-section.
 12. The buckling restrained brace as claimed in claim 9, wherein said intermediate segment of said middle section of said axial member is formed with an elongated slot extending in the axial direction.
 13. The buckling restrained brace as claimed in claim 9, wherein said restraining unit includes a rigid surrounding member surrounding said axial member and having an inner surrounding surface that faces said axial member, each of said first and second coupling sections of said axial member having opposite distal edges in the second transverse direction that are in contact with said inner surrounding surface of said surrounding member.
 14. The buckling restrained brace as claimed in claim 1, wherein said middle section of said axial member has a first lateral segment interconnecting integrally said first coupling sections to form a first plate, and a second lateral segment spaced apart from said first lateral segment in the first transverse direction and interconnecting integrally said second coupling sections to form a second plate.
 15. The buckling restrained brace as claimed in claim 14, wherein: each of said first coupling sections of said axial member has a maximum width in a second transverse direction transverse to the axial direction and the first transverse direction that is larger than that of said first lateral segment of said middle section of said axial member, and a converging part that is connected integrally to said first lateral segment and that converges toward said first lateral segment; and each of said second coupling sections of said axial member has a maximum width in the second transverse direction that is larger than that of said second lateral segment of said middle section, and a converging part that is connected integrally to said second lateral segment and that converges toward said second lateral segment.
 16. The buckling restrained brace as claimed in claim 14, wherein said restraining unit includes a rigid surrounding member surrounding said axial member and having an inner surrounding surface that faces said axial member, each of said first and second coupling sections of said axial member having opposite distal edges in the second transverse direction that are in contact with said inner surrounding surface of said surrounding member.
 17. An axial member adapted for use in a buckling restrained brace, the buckling restrained brace to be connected fixedly between two connecting plates of a framework of a building and including a rigid restraining unit that extends in an axial direction and that has opposite longitudinal ends, said axial member comprising: a middle section extending in the axial direction and adapted to be surrounded by the restraining unit; a pair of first coupling sections connected respectively and perpendicularly to opposite longitudinal end portions of said middle section, each of said first coupling sections extending in the axial direction, having at least a portion adapted to be exposed from a respective one of the longitudinal ends of the restraining unit, and being formed with a first coupling groove adapted for engaging a respective one of the connecting plates; and a pair of second coupling sections that are connected respectively and perpendicularly to said opposite longitudinal end portions of said middle section, each of said second coupling sections extending in the axial direction, being spaced apart from a corresponding one of said first coupling sections in a first transverse direction transverse to the axial direction, having at least a portion adapted to be exposed from a respective one of the longitudinal ends of the restraining unit, and being formed with a second coupling groove adapted for engaging a respective one of the connecting plates.
 18. The axial member as claimed in claim 17, wherein: said middle section is formed as an elongated plate, said elongated plate being formed with first and second side surfaces that are opposite to each other in a second transverse direction transverse to the axial direction and the first transverse direction; and each of said first and second coupling sections has a first coupling segment that is connected to said first side surface of said middle section, and that has an exposed part to be exposed from a corresponding one of the longitudinal ends of the restraining unit, and a second coupling segment that is connected to said second side surface of said middle section, and that has an exposed part adapted to be exposed from a corresponding one of the longitudinal ends of the restraining unit, and cooperating with said exposed part of said first coupling segment to define a corresponding one of said first and second coupling grooves.
 19. The axial member as claimed in claim 18, wherein each of said first and second coupling segments of said first and second coupling sections further has a connecting part connected to said exposed part of a corresponding one of said first and second coupling segments and to be surrounded by the restraining unit.
 20. The axial member as claimed in claim 19, wherein said connecting part of each of said first and second coupling segments of said first and second coupling sections has an end surface opposite to said exposed part of a corresponding one of said first and second coupling segments in the axial direction and inclining toward said exposed part of the corresponding one of said first and second coupling segments.
 21. The axial member as claimed in claim 18, wherein said end portions of said middle section are opposite to each other in the axial direction and are to be exposed respectively from the longitudinal ends of the restraining unit.
 22. The axial member as claimed in claim 21, wherein said middle section further has a main portion disposed between said end portions, and two converging portions, one of said converging portions interconnecting said main portion and one of said end portions, the other one of said converging portions interconnecting said main portion and the other one of said end portions, each of said converging portions converging from a corresponding one of said end portions toward said main portion.
 23. The axial member as claimed in claim 18, the restraining unit including a rigid surrounding member to surround said axial member, the surrounding member having an inner surrounding surface to face said axial member, wherein each of said first and second coupling segments of said first and second coupling sections is adapted to be in contact with the inner surrounding surface of the surrounding member.
 24. The axial member as claimed in claim 17, wherein said middle section has an intermediate segment and first and second lateral segments connected respectively to opposite lateral ends of said intermediate segment in the first transverse direction, said first lateral segment interconnecting integrally said first coupling sections, said second lateral segment interconnecting integrally said second coupling sections.
 25. The axial member as claimed in claim 24, wherein: each of said first coupling sections has a maximum width in a second transverse direction transverse to the axial direction and the first transverse direction that is larger than that of said first lateral segment of said middle section, and a converging part that is connected integrally to said first lateral segment and that converges toward said first lateral segment; and each of said second coupling sections has a maximum width in the second transverse direction that is larger than that of said second lateral segment of said middle section, and a converging part that is connected integrally to said second lateral segment and that converges toward said second lateral segment.
 26. The axial member as claimed in claim 24, wherein each of said first and second lateral segments of said middle section is connected perpendicularly to said intermediate segment of said middle section such that said middle section has an H-shaped cross-section.
 27. The axial member as claimed in claim 24, wherein said intermediate segment of said middle section is formed with an elongated slot extending in the axial direction.
 28. The axial member as claimed in claim 24, the restraining unit including a rigid surrounding member to surround said axial member, the surrounding member having an inner surrounding surface to face said axial member, wherein each of said first and second coupling segments of said first and second coupling sections is adapted to be in contact with the inner surrounding surface of the surrounding member.
 29. The axial member as claimed in claim 17, wherein said middle section has a first lateral segment interconnecting integrally said first coupling sections, and a second lateral segment spaced apart from said first lateral segment in the first transverse direction and interconnecting integrally said second coupling sections.
 30. The axial member as claimed in claim 29, wherein: each of said first coupling sections has a maximum width in a second transverse direction transverse to the axial direction and the first transverse direction that is larger than that of said first lateral segment of said middle section, and a converging part that is connected integrally to said first lateral segment and that converges toward said first lateral segment; and each of said second coupling sections has a maximum width in the second transverse direction that is larger than that of said second lateral segment of said middle section, and a converging part that is connected integrally to said second lateral segment and that converges toward said second lateral segment.
 31. The axial member as claimed in claim 29, the restraining unit including a rigid surrounding member to surround said axial member, the surrounding member having an inner surrounding surface to face said axial member, wherein each of said first and second coupling sections of said axial member has opposite distal edges in the second transverse direction that are adapted to be in contact with the inner surrounding surface of the surrounding member.
 32. A method of making a buckling restrained brace, comprising the steps of: (A) preparing a hollow surrounding member; (B) preparing an axial member that extends in an axial direction and that includes a middle section formed as an elongated plate and having opposite longitudinal end portions and first and second side surfaces that are opposite to each other in a transverse direction transverse to the axial direction, and two pairs of first coupling segments, each pair of the first coupling segments extending in the axial direction and being connected to the first side surface of the middle section at a respective one of the longitudinal end portions of the middle section, each of the first coupling segments having an exposed part, and two pairs of second coupling segments, each pair of the second coupling segments extending in the axial direction, and being connected to the second side surface of the middle section at a respective one of the longitudinal end portions of the middle section, each of the second coupling segments having an exposed part that cooperates with the exposed part of a corresponding one of the first coupling segments to define a coupling groove therebetween; and (C) extending the axial member through the surrounding member such that the exposed parts and the coupling grooves of the first and second coupling segments are exposed from the surrounding member.
 33. The method as claimed in claim 32, wherein: each of the first and second coupling segments further has a connecting part connected to the exposed part of a corresponding one of the first and second coupling segments in step (B); and in step (C), the connecting parts of the first and second coupling segments are surrounded by and are in contact with an inner surrounding surface of the surrounding member.
 34. The method as claimed in claim 32, wherein, in step (B), each of the first coupling segments is connected perpendicularly to the first side surface of the middle section, and each of the second coupling segments is connected perpendicularly to the second side surface of the middle section.
 35. The method as claimed in claim 32, further comprising the step of: (D) filling a curable material between the surrounding member and the axial member.
 36. A method of making a buckling restrained brace, comprising the steps of: (A) preparing a hollow surrounding member; (B) preparing an axial member that includes an intermediate segment extending in an axial direction, and first and second plates connected perpendicularly and respectively to opposite lateral ends of the intermediate segment in a first transverse direction transverse to the axial direction, each of the first and second plates having an axial length longer than that of the intermediate segment, and including two coupling sections formed respectively at opposite ends thereof in the axial direction, each of the coupling sections of the first and second plates being formed with a coupling groove; and (C) extending the axial member through the surrounding member such that a portion of each of the coupling sections and the coupling grooves of the first and second plates are exposed from the surrounding member.
 37. The method as claimed in claim 36, wherein, in step (B), the intermediate segment of the axial member is formed with an elongated slot extending in the axial direction.
 38. The method as claimed in claim 36, wherein, in step (C), the surrounding member has an inner surrounding surface that faces the axial member, each of the coupling sections of the axial member having opposite distal edges in a second transverse direction transverse to the axial direction and the first transverse direction that are in contact with the inner surrounding surface of the surrounding member.
 39. The method as claimed in claim 36, further comprising the step of: (D) filling a curable material between the surrounding member and the axial member.
 40. A method of making a buckling restrained brace, comprising the steps of: (A) preparing a hollow surrounding member; (B) preparing an axial member that includes first and second plates extending in an axial direction and spaced apart from each other in a first transverse direction transverse to the axial direction, each of the first and second plates including two coupling sections formed respectively at opposite ends thereof in the axial direction, each of the coupling sections of the first and second plates being formed with a coupling groove; and (C) extending the axial member through the surrounding member such that a portion of each of the coupling sections and the coupling grooves of the first and second plates are exposed from the surrounding member.
 41. The method as claimed in claim 40, wherein, in step (C), the surrounding member has an inner surrounding surface that faces the axial member, each of the coupling sections of the axial member having opposite distal edges in a second transverse direction transverse to the axial direction and the first transverse direction that are in contact with the inner surrounding surface of the surrounding member.
 42. The method as claimed in claim 40, further comprising the step of: (D) filling a curable material between the surrounding member and the axial member. 